1. Field of the Invention:
The present invention relates generally to an impact crushing machine for crushing rocklike materials, such as rocks, ores and clinker, and, more particularly, to an impactor for such an impact crushing machine, having strikers resistant to wear and capable of being replaced by new ones when worn out.
2. Description of the Prior Art:
FIG. 21 illustrates a conventional impact crushing machine 1. A rocklike material fed through a feed opening 2 formed in one side of the upper part of the impact crushing machine 1 into a crushing chamber 3 is struck and crushed by strikers 6 fixedly attached to the periphery of a rotor 5 rotatively supported on a main shaft 4. Pieces of the rocklike material sent flying by the rotor 5 collide against and are crushed into smaller pieces by a liner 7a attached to a first inpact plate liner 7 provided in the upper section of the crushing chamber 3. The pieces of the rocklike material repulsed by the first inpact plate liner 7 are struck further by the strikers 6. Then, some of the pieces of the rocklike material repulsed by the first inpact plate liner 7 and struck further by the strikers 6 are sent flying again against a liner 8a of a second inpact plate liner 8 provided in the upper section of the crushing chamber, whereby the pieces of the rocklike material are crushed further into finer pieces.
The conventional impact crushing machine employs solid strikers 6 formed of a hard metal such as a high chromium cast iron, a high manganese steel or a chromium-molybdenum steel. However, since the rocklike material subjected to crushing includes hard mineral pieces, the strikers 6 are worn gradually as shown in FIGS. 22(a), 22(b), 22(c) and 22(d) by the frequent impact of the hard mineral pieces on the strikers 6. That is, the striking end 6a of the striker 6 originally having an angular shape as indicated by solid lines in FIG. 22(a) is worn and rounded gradually as indicated by broken lines in FIG. 22(b).
Since it is economically disadvantageous to throw away the striker 6 worn in a shape as shown in FIG. 22(b), Japanese Patent Provisional Publication (Kokai) No. 58-174245 discloses an impact crushing machine in which the worn striker as shown in FIG. 22(b) is turned over for reuse in a position as shown in FIG. 22(c) and is used until the same is worn in shapes indicated by broken lines in FIG. 22(d) or a worn striker is inverted upside down for reuse.
Japanese Patent Provisional Publication (Kokai) No. 58-15079 discloses an impact crushing machine employing strikers each coated with an abrasion-resistant ceramic material to improve the abrasion resistance of the striker.
However, since the striker employed in the conventional impact crushing machine is not sufficiently abrasion-resistant, the striking end of the striker is worn round in a short period of use to strike rocklike pieces obliquely deteriorating the crushing ability of the impact crushing machine. Moreover, since the striker employed in the conventional impact crushing machine is a solid member, the worn striker must be replaced wholly by a new one, which requires an increased operating cost. Furthermore, the worn striker is replaced by a new one, or is turned over or inverted for reuse, for example, every one and half or three months when used for crushing rocks to produce aggregate. However, since the striker weighs about 100 kg, the replacement of the worn striker with a new one, or turning over or inverting the worn striker requires hard work.
The striker employed in the impact crushing machine disclosed in Japanese Patent Provisional Publication No. 58-15079 is provided with a abrasion-resistant chip, such as a hard ceramic chip or a hard metal chip. However, this striker has problems in that the striker must wholly be replaced with a new one when the abrasion-resistant chip is broken and that the hard metal chip is expensive and uneconomical. Accordingly, this striker is not applied practically to a heavy impact crushing machine.